Thumbstick attachment



FIG. 1 is a top perspective view of a thumbstick attachment showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines shown in the drawings depict portions of the thumbstick attachment and form no part of the claimed design. 

CLAIM The ornamental design for a thumbstick attachment, as shown and described. 